Electrical device



Oct. 5, 1965 w. M. HUMMEL ELECTRICAL DEVICE Filed March 18, 1963 INVENTOR. I V Zsig M Hummefl.

x7 673W) (241W United States Patent 3,210,714 ELECTRICAL DEVICE Wiley M. Hummel, Prophetstown, 111., assignor to General Electric Company, a corporation of New York Filed Mar. 18, 1963, Ser. No. 265,665 Claims. (Cl. 338301) The present invention relates to electrical devices such as heating devices, and more particularly to resistance heating devices.

An important object of the present invention is to provide a new and improved electrical device which is economically constructed and efficient in operation.

Another object of my invention is to provide an improved electrical device which incorporates a simplified and dependable means for terminating a conductor thereof.

An additional object of my invention is to provide a new and improved means for efiiciently connecting one end of a wire to a terminal.

In carrying out my invention, in one form thereof I have provided a heating device which includes a relatively flat elongated support and a relatively thin heating conductor spirally wound upon the support. Near each end of the support a strip of flexible insulating tape is partially wrapped around some of the end turns of the heating conductor. Each strip of tape also covers a loop in an end portion of the heating conductor, which loop extends longitudinally away from the end turns, and it is partially wrapped around the support itself. A stranded bare conductor relatively thicker than the heating conductor is looped around the strip of tape near each end of the support. The loop of this stranded conductor is disposed transversely to the longitudinal axis of the support and it overlies the longitudinal loop of the heating conductor. A shorter bare end of the stranded conductor is securely wound around an adjacent longer length of the conductor to form a twisted junction that extends transversely to the longitudinal axis of the support. By forming this twisted junction, the stranded conductor is effectively secured to the support, and at the same time, the loop of the heating conductor is held into engagement with the support by the loop of the stranded conductor. With such an arrangement, each bare end of the relatively thin heating wire is wound into mechanical engagement with the twisted junction of an associated stranded and looped conductor. Each twisted junction of the stranded conductor and the heating wire is thereupon welded to provide positive electrical engagement of the two conductors with each other. Such an arrangement provides a simplified and effective means and method for terminating an electrical heater.

Further aspects of my invention will become apparent hereinafter, and the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which I regard as my invention. The invention, however, as to organization and method of utilization, together with further objects and advantages thereof, may best be understood by reference to the following description when taken in conjunction with the accompanying drawing in which:

FIG. 1 illustrates a perspective view of a mandrel mounted heating device which is to be subsequently terminated in accordance with the present invention;

FIG. 2 illustrates a fragmentary perspective view of the device of FIG. 1, after the attachment thereto of a stranded lead which serves as part of a termination for the heating conductor;

FIG. 3 is a fragmentary perspective view similar to FIG. 2, and illustrating the mode of attachment of a 3,210,714 Patented Oct. 5, 1965 welding clip to the juncture of the stranded lead and the heating conductor.

FIG. 4 is a perspective view of a terminated heating device, in accordance with my invention; and

FIG. 5 is a sectional view taken generally along the line 5-5 of FIG. 4.

Referring first to FIG. 1 of the drawing, there is illustrated an electrical heating structure 1 which is mounted on an elongated mandrel 3. The structure 1 generally comprises an elongated tube of insulating material 5 surrounding the mandrel 3 for the major portion thereof, and a heating conductor 7 spirally wound upon the tube '5.

As further shown in FIG. 1, the mandrel 3 has a flat and rectangular cross section. Tube 5 is constructed of an insulating material such as Teflon, and is in the form of an extruded fiat oval shaped sleeve having relatively thin walls which surround the mandrel 3, as shown in FIGS. 1 and 5. The heating conductor 7 comprises a plurality of turns of insulated wire which are precision wound on and supported by the insulating tube 5 to form a heating section '8, as shown in FIG. 1.

Turning now to a significant aspect of my invention, which concerns a new and improved means and method for terminating the heating conductor 7, as shown in FIG. 1 each end portion of the heating conductor 7 is bent over and away from the longitudinal center of the heating conductor, in a direction generally parallel to the longitudinal axis of the mandrel 3. A strip of flexible insulating tape 9, such as for example, fiberglass tape is then pressed initially into engagement with the parallel conductor sections of several of the end turns of the heating conductor 7, and the adjacent portion of the tube 5 so that it covers and positions the bent over longitudinal section 11 of the conductor near its end. The end portion of the conductor 7 is then looped over at 13 and doubled back upon itself by extending portion 15 back toward the center of the conductor in a direction generally parallel to the longitudinal axis of the mandrel 3. The doubled over section 15 is then on the outer surface of the beginning part of tape 9. Tape 9 is then wrapped completely around the end turns, and the adjacent part of tube 5 and overlapped upon the doubled over section 15 of the conductor. Thus, as shown in FIG. 1, the tape 9 overlaps itself in such a manner that the starting portion of the tape 9 is threaded through the loop 13, and the doubled over section 15 of the conductor wire 7 is arranged between an outer surface of the tape 9 and an overlapped part of the tape 9.

For terminating the stripped ends 7a of the heating conductor 7 as shown in FIGS. 2 and 4, a pair of stranded leads 17 are utilized. As illustrated in FIG. 2, conductor 17 is substantially bare, is first looped around the tape 9, and is positioned adjacent to a shoulder 21 of the tape 9. Shoulder 21 is formed by the stretching of the tape 9 at the end-most turn of the heating conductor 7 (i.e., between the end-most turn and the adjacent uncovered surface of the tube 5). The loop 19 of stranded bare conductor 17 is thus positioned around the taped section of the device (as shown in FIG. 2) just beyond the last turn of heater conductor 7 and a relatively short end portion 23 of the stranded conductor 17 is thereupon securely twisted around an adjacent portion 25 of the longer length of the stranded conductor 17.

As shown in FIG. 2, when the shorter end 23 of the stranded conductor 17 is twisted, there is formed a tightly twisted electrical connection or junction 27 of the shorter portion 23 of the lead with the longer portion 25 thereof. By means of the twisted junction 27, the loop 19 is tightly secured around the folded over tape 9. Since the loop 19 of conductor 17 is arranged in transverse relationship to the longitudinal loop 13 of the heater conductor 7,

it also compresses the looped end 13 of the heating conductor 7 into engagement with the tube 5. It will thus be understood that by twisting the stranded conductor 17, this conductor has been securely arranged upon the tube 5 and tape 9, and at the same time the looped end 13 of the insulated heating conductor 7 has been additionally secured into compressive engagement with its supporting tube 5.

After the twisted junction 27 has been formed upon the stranded conductor lead 17, the end portion of stripped heater conductor 7a is then doubled back again and wound around the twisted junction 27, in the manner illustrated in FIG. 2. More particularly, the stripped end portion 7a of the heating wire 7 is preferably wound around the twisted junction in the same direction as the direction of twisting of shorter end 23 of conductor 17, and at substantially the same pitch as the twisted junction so that the turns 7b of the stripped conductor 7a are approximately disposed between adjacent turns 17a of the twisted junction of the conductor 17. It will thus be seen that I have provided a simplified means for facilitating the mechanical connection and cooperation of the stripped conductor 7a of relatively small diameter with a stranded lead 17 of larger diameter.

After the stripped heater wire 7a has been wound into mechanical engagement with the twisted junction 27 of the conductor 17, as suggested by FIG. 3, a crimping clip 29 is thereupon mechanically crimped into engagement with the twisted junction 27, and the turns 7b of the stripped end portion 7a of heating conductor 7 (see also FIG. 4). Preferably, in the illustrated heating device, the clip 29 is placed as close as possible to the tape 9 and engulfs a substantial portion of the twisted junction. As shown in FIG. 4, the clip 29, the twisted junction 27, and stripped turns 7b of the heating conductor 7 are all then welded together to form a good and positive electrical connection and termination for each end of the heating conductor 7.

While the terminated heating device, as shown in FIG. 4, is positioned on a supporting mandrel 3, it will be understood by those skilled in the art, that mandrel 3 may be readily removed from tube 5, and an elongated bimetallic member (not shown) or some other thermally responsive member may be extended through the tube to provide a thermal timing device.

It will now, therefore, be seen that my new and improved electrical device, as herein illustrated for an electrical resistance heater, are both eflficient and advantageous. In view of the simplified construction of this device and its eflicient mode of termination, it has been found to be very economical to manufacture.

While in accordance with the patent statutes I have described what at present is considered to be the preferred embodiment of my invention it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from my invention, and I, therefore, aim in the following claims to cover all such equivalent variations as fall within the true spirit and scope of this invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electrical heating device comprising a flat elongated element of substantially rigid material, a tube of insulating material substantially surrounding said element and generally conformant to the size thereof, a heating conductor wound around said insulating tube and having its ends remotely disposed, a strip of insulating tape wrapped around said tube and said heating conductor near each end of the heating condutcor, a stranded wire lead looped around each strip of insulating tape, each said lead being mechanically secured to the tape by means of an uninsulated twisted junction of one end of the lead and an adjacent longer portion thereof, said heating conductor having a smaller diameter than the stranded conductor and including bare ends wound into cooperative l engagement with the twisted junction of each stranded wire lead, the twisted junctions of said stranded wire leads and the bare ends of said heating conductor being Welded into positive electrical engagement.

2. An electrical heating device comprising an elongated insulative support, a heating conductor of relatively thin wire wound upon said support to form a heating section, said heating conductor having a plurality of end portions, at least one of said end portions of said heating conductor positioned adjacent one end of said heating section and curving partially toward the other end of said heating section, a stranded bare conductor having an uninsulated first portion formed into a loop near one end thereof encircling the support in the vicinity of the curving end portion of said heating conductor, said stranded conductor including a second portion of the same general diameter as the first portion thereof extending generally away from the support, said loop of said stranded conductor being mechanically secured to the support by means of an uninsulated twisted junction of one end of said first portion of the stranded conductor with another part of said first portion, said loop overlying said curving end portion of said heating conductor thereby to compress said curving end portion firmly in place on said support, an uninsulated section of the end portion beyond the curve of said heating conductor being wound into cooperative engagement with the twisted junction of the stranded conductor, and means for electrically joining said twisted junction into positive electrical engagement with the uninsulated section of said heating conductor.

3. The device of claim 2 wherein a strip of flexible insulating tape is conjointly wrapped and overlapped around said support and end turns of said heater conductor adjacent said curving end portion thereof, with a part of the strip being between said loop of the stranded conductor and said support thereby to position the curving end portion of said heating conductor on said support.

4. An electrical device comprising support means; a first electrical conductor of preselected diameter having a first portion formed into a loop near one end thereof positioned tightly around said support means, with the end of said first portion being twisted into a firm mechanical and electrical junction with another part of said first portion; a second portion of said first electrical conductor formed with the same diameter as said first portion extending away from said support means; a second electrical conductor of smaller diameter than said first electrical conductor having one end thereof wound into cooperative electrical and mechanical engagement With the twisted junction of said first electrical conductor, with said loop retaining a part of said second electrical conductor adjacent the one end thereof in position relative to said support means and said twisted junction; and a clip crimped over said twisted junction firmly securing the one end of said second electrical conductor and said twisted junction together.

5. An electrical device comprising support means; a first electrical conductor having a plurality of turns encircling said support means to form a heating section thereon; said first electrical conductor terminating in end portions, with one of said end portions positioned adjacent one end of said heating section; means tightly covering the one end of said heating section, a part of said support means, and a part of the one end portion of said first electrical conductor while leaving the central part of said heating section unobstructed; a second electrical conductor having a first portion formed into a loop encircling the covering means and a second portion projecting away from said first electrical conductor, the termination of said loop being electrically connected to another part of said first portion, with the loop extending tightly around said covering means; and the one end portion of said first electrical conductor being attached to the electrical connection of said second electrical conductor adjacent said covering means whereby the end 5 portion of the first electrical conductor is electrically connected to said second conductor and is firmly secured along with the one end of said heating section onto the support means in the vicinity of the electrical connection of the loop.

References Cited by the Examiner UNITED STATES PATENTS Dowsett et a1 29-155 .68 Masin 338-265 Bullinger 338-266 Mead 338-301 Siegel 338-266 Jagger 338-296 X Ganci 338-266 Cerny 29-155.68 Eaves 338-264 X Bourns et a1. 338-301 RICHARD M. WOOD, Primary Examiner. 

1. AN ELECTRICAL HEATING DEVICE COMPRISING A FLAT ELONGATED ELEMENT OF SUBSTANTIALLY RIGID MATERIAL, A TUBE OF INSULATING MATERIAL SUBSTANTIALLY SURROUNDING SAID ELEMENT AND GENERALLY CONFORMANT TO THE SIZE THEREOF, A HEATING CONDUCTOR WOUND AROUND SAID INSULATING TUBE AND HAVING ITS ENDS REMOTELY DISPOSED, A STRIP OF INSULATING TAPE WRAPPED AROUND SAID TUBE AND SAID HEATING CONDUCTOR NEAR EACH END OF THE HEATING CONDUCTOR, A STRANDED WIRE LEAD LOOPED AROUND EACH STRIP OF INSULATING TAPE, EACH SAID LEAD BEING MECHANICALLY SECURED TO THE TAPE BY MEANS OF AN UNISULATED TWISTED JUNCTION OF ONE END OF THE LEAD AND AN ADJACENT LONGER PORTION THEREOF, SAID HEATING CON- 